1878.] 



Bacterium termo and Micrococcus. 



477 



Effects of Desiccation and of different Temperatures on Bacterium termo 



and Micrococcus. 



If the oil be removed by blotting paper from between the glass ring 

 and the covering-glass of a preparation made as above described, or if 

 the covering-glass be fractured without being displaced, the cultivation 

 liquid rapidly evaporates, and the remains of what a few minutes 

 before were active organisms are in great part left adhering to the 

 under surface of the covering-glass. Preparations treated in this way 

 may be either subjected to high or low temperatures ; or, when protected 

 by a glass cap, may be left in the ordinary atmosphere. The result of 

 desiccation was ascertained by infecting flasks containing sterilized 

 organic infusions. Such flasks infected with rods desiccated at 20° C. 

 remain sterile, but flasks infected with desiccated spores soon teem with 

 Bacteria, and flasks infected with desiccated Micrococci soon teem with 

 round, oval, and dumbbell-shaped organisms, leading to the conclusion 

 that desiccation destroys Bacterial rods ; but that, though continued 

 for weeks, it has no influence on spores or Micrococci. If Micrococci 

 and the spores of B. termo are not destroyed by desiccation in a small 

 protected atmosphere, it may be further inferred that they retain their 

 viability when dried in the ordinary atmosphere, and, being extremely 

 small and light, that after they are dry they will float about along 

 with other solid particles in disturbed, and settle down in quiet, atmos- 

 pheres, without undergoing any change until they find themselves in a 

 medium which admits of their growth and development. In all pro- 

 bability desiccation destroys the oval and dumbbell-shaped forms of 

 Micrococcus, the round spore-like forms only retaining their vitality. 

 That spores exist in our ordinary atmosphere may be easily proved by 

 placing sterile organic infusions in different parts of a building. In 

 such a building as University College a considerable number of 

 different organisms may be found. In cold rooms the infusions may 

 remain sterile for a considerable time, but generally a scum soon 

 appears on the surface, which, on examination, may contain, besides 

 Bacteria, fungi, monads, and other low forms from both the animal and 

 vegetable kingdom. However readily the unprotected rods of Bacteria 

 are destroyed when desiccated at a temperature of 30° C, they are not 

 destroyed in the substance of a spleen or kidney when the temperature 

 is raised to 40° C. Those in the outer part of the dried portion of 

 spleen or kidney are destroyed, but those in the centre are protected 

 by the hard outer cake, not only because this hard shell tends to keep 

 the heat from them, but especially because it tends to prevent complete 

 desiccation. 



Effects of Ebullition. 



Along with Dr. Burdon Sanderson,* I have shown that the spores 

 * " Quart. Journ. Micro. Science," April, 1878. 



